Despite recent warnings from prominent Democrats, such as Newark Mayor Cory Booker and former President Bill Clinton, that attacks on presumptive Republican presidential nominee Mitt Romney’s record as head of private equity firm Bain Capital might be not only inappropriate but also ineffective, Priorities USA Action, a pro-Obama Super PAC is back at it with a new ad denouncing Romney’s financial vampirism.

In the new ad, Donnie Box, “a former worker,” who stands outside a plant allegedly closed by Bain’s predatory practices, assures voters that “Romney and Bain Capital shut this place down;” adding that the promises of preserving “health care packages” and “retirement programs” were broken.

The ad marks a return to the Bain Capital narrative, after Booker (who was subsequently castigated by his party) and Clinton (who somewhat apologized afterwards) raised their voices of dissent. It is unclear if this is a strategy that the Obama campaign, which steered away from it and focused on Mitt Romney’s jobs record as governor of Massachusetts instead, approves; since the clip was created by a super PAC and candidates are forbidden by law to have any contact with these entities.

The case mirrors the recent Republican presidential primary where candidates Mitt Romney, Newt Gingrich and Rick Santorum were forced to explain debate after debate that the often personal and nasty attack ads released by super PACs that supported them were out of their reach.

And speaking of Romney, the former governor released a statement in response to the pro-Obama super PAC ad:

“Another day, another misleading attack from President Obama’s allies. President Obama thinks the economy is ‘doing fine,’ in spite of the fact that 23 million Americans are struggling for work, incomes have fallen and America is drowning in debt. President Obama’s own supporters – even former President Clinton – have criticized these distorted attacks on free enterprise, calling them ‘nauseating’ and ‘unfair.’ Unlike President Obama, Mitt Romney has the record and pro-growth plan to fix the economy and get our country back on the right track.”